Biofermentation of organic waste from a pig-breeding complex in a drum-type installa-tion

Abstract

Relevance. In modern pig-breeding complexes, manure is processed by separation producing the liquid and solid manure fractions. The complexes also generate other types of organic waste. Testing the process of producing the organic fertilizer based on the solid organic waste of a pig-breeding complex in a drum-type biofermenter.Material and methods. The processing of a mixture of two types of solid fractions of pig slurry and the waste from mechanical cleaning of grain into an organic fertilizer in a drum-type biofermentation unit was tested. The tested material was produced on the pig-breeding complex with the closed production cycle located in Leningrad Region. The optimization criterion was the temperature of the mixture in the installation. The controlling factors were the aeration frequency, the air supply rate to the biofermenter, and the rotation interval of the drum. Assumed values of the tested factors were: the moisture content of the mixture of 55–65% and the density of the mixture of 400– 600 kg/m3. The standard methods for statistical and experimental data analysis were applied.Results. Four operation modes of the biofermenter were tested, of which only one allowed to achieve the heating of the mixture above 55 °C and a stable course of the biofermentation process. Under this mode, the aeration rate was 5 min/h; the air supply rate to the biofermenter was 10 m/s; and the drum rotation interval was every 12 hours. The significance of the factors in a multivariate experiment was considered; the mathematical model was analyzed using the steepest ascent method. Considering the identified operation mode, 12 drum-type biofermenters with the working volume of 31.3 m3 each will be needed to process the solid fraction of manure produced on the pig-breeding complex with the animal stock of 107,000 head and the output of the solid fraction of manure of 90 tons per day. A building with a floor area of 1000 m2 will be required to place these biofermenters. This area is 113.4 times smaller than the area of the watertight pad for clamps to process the manure by the passive composting technology. Nitrogen emissions will be reduced by 6.3% owing to the intense mineralization of nitrogen in the fermented mixture.